Botutinum neurotoxin, released as a protein complex called progenitor toxin by the bacterium Clostridium botulinum, causes the disease botulism that is of considerable concern because of its high mortality rate when not treated immediately and properly. It is also a potential biowarfare threat. Its potential use in bioterrorism makes it imperative to develop measures to protect the armed forces and the public in general. The overall objective of this proposal is to aid in developing and designing such measures viz., medicines and vaccines. The long-range goal is to achieve this by understanding the function and purpose of the assembly of the components of C. botutinum progenitor toxins, complex formed by neurotoxin and other associated proteins, by determining the three-dimensional structure of progenitor toxin B via X-ray crystallography. It is believed that progenitor toxins protect the botulinum neurotoxin from the harsh conditions of low pH and peptidases present in the gastrointestinal tract. Knowledge of the three-dimensional organization of these proteins and their interactions with the neurotoxin and one another will lead to the understanding of the mechanism by which they protect the neurotoxin. Progenitor toxin's ability to be absorbed from the gut with minimum degradation makes it a suitable candidate for use as a carrier of oral medicines by appropriate modification of the toxin molecule. Additionally, it will help in designing oral vaccines for many afflictions besides botulism and tetanus. This is particularly important when a large population including animals and birds is to be vaccinated. The short-range goals are to crystallize M and L forms of progenitor toxin B for X-ray diffraction analysis and initiate structural analysis when crystals are obtained. The individual specific aims leading to the overall goal are listed below. 1. To crystallize M and L forms of C. botulinum progenitor toxin B for three-dimensional structure determination via X-ray crystallography. 2. To measure the mass of the progenitor complex with the use of the STEM facility at Brookhaven National Laboratory. 3. To obtain preliminary crystal data from the crystals of M and L forms of progenitor toxin B.